Electron discharge device



y 1934- H. w. PARKER ELECTRON DISCHARGE DEVICE Filed Dec. 15, 1932 lNVENTOR Henrg W Parker I ATTORNEY Oil Patented May 15, 1934 PATENT QFFICE ELECTRON DISCHARGE DEVICE Henry W. Parker, Toronto, Ontario, Canada, as-

slgnor to Rogers Radio Tubes, Limited, Toronto,

Ontario, Canada, Canada a corporation of Ontario,

Application December 13, 1932, Serial No. 646,970

3 Claims.

My invention relates to electron discharge devices and pertains more especially to that class of such devices as termed thermionic tubes.

It has long been known that electrostatic fields set up by the potentials applied to the electrodes within such electron discharge devices extend beyond the confines of the envelopes enclosing the electrodes an that such stray fields interfere with the proper operation of adjacent cooperating tubes and decrease the effective and eiiicient operation of the organization utilizing the tubes.

Many expcdients have been employed to eliminate such interference such as enclosing the tube in a metal container or coating the tube envelope with a conductive coating. This latter method is the most practical because the more economical and it is coming into extensive usev I have found, however, that coating only the envelope of the tube with a conducting material does completely shield adjacent tubes and apparatus in the efiects of stray fields due to the bfiS applied to the electrodes within the tube, espec -y the anode potentials. I have discovered that a considerable stray field emanates from. that portion of the anode lead extending from the bottom of the tube envelope through the tube base to the contact prongs mounted therein. I have found that the stray field from this portion of the anode lead in modern tubes is sufficient to cause very undesirable interference with adjacent tubes and adjacent apparatus and that such fields materially lessen the effective and efiicient operation of the apparatus employing the tube.

I have discovered that if the wall surface of the base of the tube, which is almost invariably formed of non-metallic or insulating material, is completely coated with a conducting material, which likewise covers the surface of the tube envelope, that every vestige of stray field is eliminated and that in a tube so coated the fields produced by the potentials applied to the electrodes within the tube are wholly confined within the tube so that the tube may be used in cooperation with other tubes in electrical apparatus without causing the slightest disturbing influence.

It is an object of my invention, therefore, to provide an electron discharge device from which emanation of all disturbing stray fields is eliminated.

It is a further object of my invention to provide an electron discharge tube having a conducting coating extending from the lower edge of the tube base to a point near the top of the tube envelope whereby stray fields from the potentials applied to the electrodes within the tube are eliminated.

(Cl. 250-Z7.5)

ccompanying forming a e ication, I have illustrated a part1: sectioned ele ation of a preferred form of thermionic tube bearing my improved shield coating thereon.

Referring now to the verb e l is composed of drawing, the tube englass or other vitreous as is usual and is cemented as usual in t e base i wh ch preferably and as usual conof a bottom thereof contact prongs 5 for connecung the electrodes hin he tube to the organization utilizing the tube. control grid contact 3 is inouned on top of the tube. I prefer to apply my shield conductive c0ating 2 in the form of a metallic to the tube and base sho and I prefer to apply the coating 2 from the lower edge of the base 4 to a point near the top of the tube as indicated the drawing. A portion of the top or the tube envelope is left free from coating in order to insulate the conact terminal 3.

I prefer in order that the shield coating may be in intimate contact with the tube envelope and base to sand blast or otherwise roughen the sur fa es of the envelope and base before applying the metallic coating thereto as shown and described in my co-pending joint application with J. Eakins, Serial No. 632,506v filed September 10, 1932, entitled Automatic machine for proc essing thermionic tubes and the like, which discloses and describes machine and method of applying such. coating.

It will be noted that the conductive coating adheres intimately and closely to the surface of the tube envelope 1 and base i and conforms to the outlines thereof. It will also be noted that the coating extends in a continuous manner from a point near the top of the tube envelope 1 to the lower edge of the base 4. The coating is not applied to the bottom of the base i and in coating the care is taken to prevent any of the coating from adhering to the bottom of the base and thus lower he insulation resistance between the contact prongs 5.

It will be noted that all of the electrodes and the leads thereto are completely shielded by the extension of the coating from the upper edge of the tube base to the lower edge thereof and it will be further noted that when a tube coated mate in accordance with my invention is placed in the socket in which it is used that the electrodes within the tube are completely shielded and stray fields therefrom eliminated. It is the usual practice to mount the sockets for tubes in radio and electrical equipment on the under side of a metallic support or chassis and as usual the lower edge of the tube base 4 when the tube is in position in its socket is usually slightly below the upper surface of the metallic support for the tube sockets.

The shield coating is preferably conductively connected to the metal of the chassis and I prefer to effect such connection by means of spring clips secured to the chassis and bearing on the coated base of the tube as shown in my co-pending joint application with E. S. Rogers, Serial No. 598,154, filed March 11, 1932, entitled Thermionic tube socket. Thus, my completely shielded tube, when in place in the socket, presents an effective shield to exclude extraneous fields therefrom and thus completely eliminates interference with adjacent tubes or apparatus.

It will be further noted that my shielding accomplishes the same effective shielding as is now accomplished by cumbersome metal cases or cans. As it eliminates the extra equipment of cases or cans, it is more economical. Further, as the shielding is unitary with the tube, the tube may be replaced with confidence that the shielding effect is not lost. In the case of shielding cans or containers, these are often misplaced in replacing tubes in electrical equipment or are not properly fitted so that they cease to function efficiently.

Having thus described my invention, what I claim is new and desire to secure by Letters Patent of the United States is as follows:

1. The combination with an electron tube comprising a cylindrical insulating base member the exterior surface of which is roughened bearing contact prongs and of the type adapted to be mounted with the bottom of said cylindrical base member flush with a mounting panel, a vitreous electrode containing envelope the exterior surface of which is roughened supported by said base member and having an electrode contact terminal at the upper extremity thereof furthest from said base member, of an external metallic electrode surrounding the exterior of said envelope from an uppermost point on said envelope substantially removed from said contact terminal and forming a continuous sheath extending down to a point on said base member where said base member comes flush with its aforementioned mounting panel said metallic electrode being in intimate contact with the roughened surfaces of said electrode containing envelope and said insulating base member.

2. In an electron tube, a vitreous electrode containing envelope the exterior surface of which is roughened, and a metallic coating carried by said envelope in intimate contact with said roughened surface for preventing undesirable field effects in the electrical operation of said envelope and the electrodes therein.

3. The combination with an electron tube comprising a cylindrical insulating base member bearing contact prongs and of the type adapted to be mounted with the bottom of said cylindrical base member flush with a mounting panel, a vitreous electrode containing envelope supported by said base member and having an electrode contact terminal at the upper extremity thereof furthest from said base member and having an exterior roughened surface, of an external metallic electrode surrounding the exterior of said envelope from an uppermost point on said envelope substantially removed from said contact terminal and forming a continuous sheath extending down to a point on said base member where said base member comes flush with its aforementioned mounting panel, said sheath being in intimate contact with said roughened surface of said envelope for preventing undesirable field effects in the electrical operation of said envelope and the electrodes thereof.

HENRY W. PARKER. 

